Sound delivery systems such as public address systems are used in numerous places and situations for making announcements and/or playing background music or the like. When addressing a crowd of people within a large area, such as an indoor concourse or auditorium, echoes generated by the enclosed building create signal output interference within the area. The result is a distorted, sometimes unintelligible or otherwise poor quality audio output signal. To add to the distortion, public address systems commonly use several loudspeakers which are arranged throughout the site and which tend to interfere with each other due to arrival delays.
In a large open area, the power required to project the audio output signal throughout the entire area can result in excessive amplification and potential distortion. Outdoors, it is likely that people close to one of the speakers of the system will be exposed to an uncomfortably high output volume or sound pressure level. This high sound pressure level is necessary so that people remote from the speakers will be able to hear the audio output signal at a normal level.
Further, there has been a growing concern for noise pollution within and around residential areas. Ideally, the audio output from any sound delivery system reaches only those people within a prescribed zone and does not "leak" or escape into the surrounding area. One problem in trying to achieve such an isolated sound delivery system resides in the difficulty of controlling or directing the sound pressure pattern of each speaker or speaker unit of the system. Known sound delivery systems employ speakers which disperse sound in a conical pattern. Because each speaker also requires sufficient power to ensure that all points of a selected area are reached, it is difficult to limit the output sound to a prescribed area.
Another problem with prior art public address systems resides in the manner in which the speakers are normally mounted. In most cases, the individual speakers are placed at the most convenient locations, e.g., on the side of a building, a telephone pole, a lamp post, etc. Typically, these speakers are large, bulky and unsightly. It would be desirable to provide a public address system which discretely integrates the speakers (or speaker arrays) within the environment so that the source of sound is relatively unobtrusive, both visually and audibly.
Moreover, it is common in amusement and theme parks for an individual to address a large group of people through the public address system. If the announcer moves to a position within the vicinity of the loudspeakers, feedback between the loudspeakers and the announcer's microphone generates a high pitched "squeal" which is uncomfortable for the listeners. Electronic means may be provided to reduce the effect of the feedback but this introduces added expense and, furthermore, is not always entirely effective.
The principal objects of this invention are to provide an improved sound delivery system in which the speakers are relatively unobtrusive (i.e. "low profile) and to provide isolated adjacent sound zones".